The hybrid electric vehicle is a future vehicle that adopts an engine and also adopts a motor driving source as an auxiliary power source to promote reduction of generation of exhaust gas and to improve fuel efficiency.
A constitutional example of power transmission for a hybrid electric vehicle may be found in FIG. 8, where an engine (100), a motor (200) and an automatic transmission (300) are arranged in series on one axis, a clutch (400) is arranged between the engine (100) and the motor (200), and a high voltage battery (500) is chargeably and dischargeably connected to the motor (200) as a constitution for operating the abovementioned elements.
In a power transmission and a running mode of a hybrid electric vehicle thus configured, the running mode may include an EV (Electric Vehicle) mode (see FIG. 8a) using only a power of the motor, ab HEV (Hybrid Electric Vehicle) mode (see FIG. 8b) using an auxiliary power as a turning effect of the motor (200), an engine sole mode (see FIG. 8c) using only an engine power for running where a motor functions as a generator for battery charging, and an RB (Regenerative Braking) mode (see FIG. 8d) retrieving (recovering) braking and inertial energy of a vehicle from the motor through generation when the vehicle is braked or running by inertia to charge the energy to a battery.
The battery in the constitution of a hybrid electric vehicle that runs in the above manner may be formed in a battery pack as a unit, where as illustrated in FIG. 7, a width of a main operation area in the battery pack is considerably very narrow, whereas control of temperature for the battery pack to a predetermined level in an actually covered area has a characteristic difficulty.
Particularly, the battery pack creates a problem in a low temperature area, the reason of which is resulted from a drawback that chloridation of electrolyte is progressed quicker during charging than during discharging due to characteristic of battery.
Meantime, a motor, an inverter and a battery, among the elements of a hybrid electric vehicle, are cooled by water cooling system or air cooling system in order to cool these elements, and in case of motor, the motor is cooled by water, the inverter is cooled by water or air cooling system, and the battery is largely cooled by air cooling system. However, unlike general home electric appliances, the hybrid electric vehicle, being a machine that must be operated both in low and high temperature areas, suffers from a severer hardship from temperature changes in each element, and the battery may be the weakest element to the temperature changes. In case of operation at a high temperature (45° C.), a BCM (Battery Control Module) inside a battery module functions to protect the battery module by controlling an output, which however causes reduction in fuel efficiency of a hybrid electric vehicle, and in order to prevent the reduced fuel efficiency, an air cooling fan is employed to control a battery temperature in order to maintain a temperature of 45° C. at all times.
The most difficult problems in controlling a battery temperature occurs when the hybrid electric vehicle is operated at a low temperature area, where the battery capacity is reduced at a low temperature area, chloridation of electrolyte is progressed in response to usage, and life of battery is caused to be shortened, resulting in deterioration of durable life of battery that occupies the lion's share of material cost in the hybrid electric vehicle.
Here, an inner structure and operation of conventional battery pack will be described with reference to FIGS. 5 and 6.
Referring to FIG. 5, a circuit structure inside the conventional battery pack is largely comprised of a battery (10), a safety plug (18) and a PRA (Power Relay Assembly). To be more specific, each battery cell (12) is connected by the safety plug (18), a first main relay (21) of the PRA (20) is connected to an anode side of the battery (10), and a second main relay (22) and a current sensor (23) are connected to a cathode side of the battery (10), and an output terminal of the current sensor (23) is connected to a pre-charge relay (24).
Furthermore, the first and second main relays (21, 22) and the pre-charge relay (24) are controllably turned on and turned off by a BMS (Battery Management System, 40), which is a battery controller.
Thus, as explained in the flowchart of FIG. 6, determination is made as to whether a battery (10) temperature is a temperature capable of performing a hybrid mode operation (engine+motor assist running mode according to battery charging/discharging operations), and each relay (21, 22) is excited by the BMS (40) to implement the charging or discharging of the battery (10).
However, when there is a need of hybrid mode operation at a low temperature area in a circuit structure inside the conventional battery pack, chloridation of battery electrolyte is more quickly generated during a charging operation than in a discharging operation due to low temperature characteristic of battery to shorten life of battery, such that only an operation of re-starting the hybrid mode operation can be possible while being in a stopped state of hybrid mode operation until a battery temperature rises to a predetermined temperature, and thus, the fuel efficiency resultantly drops because the hybrid mode operation cannot be made under a low temperature state, and therefore, there is required a measure of increasing a battery temperature to a temperature where the hybrid mode operation can be started as quickly as possible at a low temperature.
Particularly, in case of hybrid commercial vehicles (buses), a battery pack is mounted at a roof side, whereby a severe heat loss of battery can be generated due to introduction of engine cooling water or heating air through an indoor duct and a pipe mounted on the roof of the vehicle.
An object of the present disclosure is to provide a battery pre-heating apparatus for hybrid electric vehicle configured to propose a battery temperature control measure at a low temperature state in order to maximize a motor assist performance at a low temperature section of a battery, and a control method thereof.
Another object is to provide a battery pre-heating apparatus for hybrid electric vehicle configured to improve fuel efficiency by normalizing a hybrid mode operation at a quicker time, and a control method thereof.
Still another object is to provide a battery pre-heating apparatus for hybrid electric vehicle configured to include a heat generating paste composition drivable at a low voltage and at a low power due to being small in resistance change to temperature and low in specific resistance, and a control method thereof.
In order to solve the technical subject, and in one general aspect of the present disclosure, there is provided a battery pre-heating apparatus for hybrid electric vehicle, the apparatus comprising: a battery comprised of a plurality of battery cells; a power relay assembly including a first main relay connected to both electrode sides for charge/discharge control of a battery; and a pre-heater including at least one plane heater formed through a heat generating paste composition to pre-heat a battery to a predetermined temperature using a power generated from regenerative braking by being connected between an output terminal of the first main relay and an output terminal of the second main relay, wherein the heat generating paste composition includes a carbon nano tube particle 3˜6 parts by weight, a carbon nanoparticle 0.5˜30 parts by weight, a mixed binder 10˜30 parts by weight, an organic solvent 29˜83 parts by weight and a dispersant 0.5˜5 parts by weight, against a heat generating paste composition 100 parts by weight, and wherein the mixed binder is mixed with epoxy acrylate, polyvinyl acetal and phenolic resin, or mixed with hexamethylene diisocyanate, polyvinyl acetal and phenolic resin.
Preferably, but not necessarily, the apparatus further comprises a pre-heating relay connected to between the output terminal of the first main relay and the pre-heater to receive control of ON/OFF by a BMS (Battery Management System).
Preferably, but not necessarily, the pre-heater may be a heating core mounted at a floor surface of a battery case encompassing a plurality of battery cells to heat a cooling fluid inside a fluid path formed at a lateral surface of the battery case.
Preferably, but not necessarily, the mixed binder may be mixed with polyvinyl acetal 10˜150 parts by weight and phenolic resin 100˜500 parts by weight, against epoxy acrylate or hexamethylene diisocyanate 100 parts by weight.
Preferably, but not necessarily, the apparatus may further comprise a silane coupling agent 0.5˜5 parts by weight against the heat generating paste composition 100 parts by weight.
Preferably, but not necessarily, the carbon nano tube particle may be a multi-wall carbon nano tube particle.
Preferably, but not necessarily, the organic solvent may be a solvent mixed with two or more substances selected from carbitol acetate, butyl carbitol acetate, DBE(dibasic ester), ethyl carbitol, ethyl carbitol acetate, dipropylene glycol methyl ether, cellosolve acetate, bytyl cellosolve acetate, butanol and octanol.
Preferably, but not necessarily, the plane heater may be formed by the heat generating paste composition being screen printed, gravure printed or comma coated on a substrate.
Preferably, but not necessarily, the substrate may be a polyimide substrate, a glass fiber mat, or a ceramic glass.
Preferably, but not necessarily, the plane heater may further include a protective layer coated on an upper surface of the plane heater and formed with an organic matter having a silica or a black pigment such as a carbon black.
Preferably, but not necessarily, the apparatus may further comprise a power supply part supplying an electric power to the plane heater.
In another general aspect of the present disclosure, there is provided a control method of a battery pre-heating apparatus for hybrid electric vehicle, the method comprising: determining whether a temperature of a battery is within a hybrid operable range; exciting a pre-heating relay to allow being turned on, the pre-heating relay being connected to between a first main relay of a power relay assembly, which is one of circuit elements inside a battery pack and a pre-heater, when the temperature of battery is in a low temperature state of being less than the hybrid operable range; supplying a power generated from a motor in response to regenerative braking of a hybrid electric vehicle to the pre-heater through the pre-heating relay; and heating each battery cell inside the battery pack to a predetermined temperature in response to operation of heated pre-heater, wherein the pre-heater includes at least one plane heater formed through a heat generating paste composition, and wherein the heat generating paste composition includes a carbon nano tube particle 3˜6 parts by weight, a carbon nanoparticle 0.5˜30 parts by weight, a mixed binder 10˜30 parts by weight, an organic solvent 29˜83 parts by weight and a dispersant 0.5˜5 parts by weight, against a heat generating paste composition 100 parts by weight, and wherein the mixed binder is mixed with epoxy acrylate, polyvinyl acetal and phenolic resin, or mixed with hexamethylene diisocyanate, polyvinyl acetal and phenolic resin.
The advantageous effect of a battery pre-heating apparatus for hybrid electric vehicle, and a control method thereof according to the present disclosure may be explained as below: that is, according to at least one of exemplary embodiments of the present disclosure, a battery temperature management measure at a low temperature state may be proposed in order to maximize a motor assist performance of hybrid at a low temperature section.
Furthermore, according to at least one of exemplary embodiments of the present disclosure, fuel efficiency may be improved by normalizing a hybrid mode operation within a fastest possible time.
Still furthermore, according to at least one of exemplary embodiments of the present disclosure, a heat generating paste composition may be included that is drivable at a low voltage and at a low power due to being small in resistance change to temperature and low in specific resistance.